add strbeg argument to Perl_re_intuit_start()

(note that this is a change both to the perl API and the regex engine
plugin API).

Currently, Perl_re_intuit_start() is passed an SV, plus pointers to:
where in the string to start matching (strpos); and to the end of the
string (strend).

Unlike Perl_regexec_flags(), it doesn't also have a strbeg arg.
Because of this this, it guesses strbeg: based on the passed SV (if its
svPOK()); or just set to strpos otherwise. This latter can happen if for
example the SV is overloaded. Note also that this latter guess is wrong,
and could in theory make /\b.../ fail.

But just to confuse matters, although Perl_re_intuit_start() itself uses
its guesstimate strbeg var, some of the functions it calls use the global
value of PL_bostr instead. To make this work, the *callers* of
Perl_re_intuit_start() currently set PL_bostr first. This is why \b
doesn't actually break.

The fix to this unholy mess is to simply add a strbeg arg to
Perl_re_intuit_start(). It's also the first step to eliminating PL_bostr
altogether.

1 files changed, 24 insertions, 3 deletions

diff --git a/pod/perlreapi.pod b/pod/perlreapi.pod
index 3d0962ac8d..c4e30cb4a8 100644
--- a/pod/perlreapi.pod
+++ b/pod/perlreapi.pod
@@ -21,6 +21,7 @@ following format:
                          void* data, U32 flags);
         char*   (*intuit) (pTHX_
                            REGEXP * const rx, SV *sv,
+			   const char * const strbeg,
                            char *strpos, char *strend, U32 flags,
                            struct re_scream_pos_data_s *data);
         SV*     (*checkstr) (pTHX_ REGEXP * const rx);
@@ -286,9 +287,14 @@ Optimisation flags; subject to change.
 
 =head2 intuit
 
-    char* intuit(pTHX_ REGEXP * const rx,
-                  SV *sv, char *strpos, char *strend,
-                  const U32 flags, struct re_scream_pos_data_s *data);
+    char* intuit(pTHX_
+		REGEXP * const rx,
+		SV *sv,
+		const char * const strbeg,
+		char *strpos,
+		char *strend,
+		const U32 flags,
+		struct re_scream_pos_data_s *data);
 
 Find the start position where a regex match should be attempted,
 or possibly if the regex engine should not be run because the
@@ -296,6 +302,21 @@ pattern can't match.  This is called, as appropriate, by the core,
 depending on the values of the C<extflags> member of the C<regexp>
 structure.
 
+Arguments:
+
+    rx:     the regex to match against
+    sv:     the SV being matched: only used for utf8 flag; the string
+	    itself is accessed via the pointers below. Note that on
+	    something like an overloaded SV, SvPOK(sv) may be false
+	    and the string pointers may point to something unrelated to
+	    the SV itself.
+    strbeg: real beginning of string
+    strpos: the point in the string at which to begin matching
+    strend: pointer to the byte following the last char of the string
+    flags   currently unused; set to 0
+    data:   currently unused; set to NULL
+
+
 =head2 checkstr
 
     SV*	checkstr(pTHX_ REGEXP * const rx);